High rates of relapse characterize drug and food addiction. Relapse is often preceded by subjective reports of intense craving and these cravings can be induced by drug or food-paired stimuli. Rats will press a lever for the presentation of a stimulus complex (a tone + light) previously associated with their food or drug taking, providing a model of cue-induced craving. We have demonstrated (Nature, 412:141-2, 2001) that responding for a stimulus previously associated with cocaine intake increases over the course of forced abstinence from self-administration (13-fold increase by 60 days of forced abstinence). We labeled the phenomenon an "incubation of craving" and have observed the effect in rats following sucrose self- administration. In recent studies, we have found that inactivation of the nucleus accumbens, a brain region involved in motivated behavior, attenuates the incubation of craving for either cocaine or sucrose. The experiments outlined in this proposal will further explore the role of the nucleus accumbens in the incubation of craving effect in sucrose-experienced animals. Dopamine and glutamate are known to functionally interact in the nucleus accumbens and have been linked to relapse behaviors. Core and shell subregion distinctions have also been made in this regard. Specifically, we propose to attempt to block the incubation of craving by challenging accumbal core and shell subregions with antagonists of dopamine and glutamate receptors at Day 1 or Day 30 of forced abstinence. All experiments in this proposal are designed to allow full participation of undergraduate and master's level students in an area of research usually reserved for Ph.D. students and post-doctoral researchers. These experiments will further our understanding of the incubation of craving effect and will influence the direction of future grant proposals from our laboratory. Information gained from this project may also provide direction for behavioral therapy and medications-based therapy for drug addiction and eating disorders. Relapse characterizes drug and food addictions. These are major public health problems. The studies in this proposal aim to identify neural substrates of relapse.